U.S. Pat. No. 3,857,398 to Rubin, entitled "Electrical Cardiac Defibrillator", describes a combined cardiac pacer and defibrillator device which performs a pacing or a defibrillating function depending on the condition detected. When the device detects tachycardia, it switches to a defibrillating mode and, after a period of time during which a charge is accumulated, delivers a defibrillation shock to the patient. When the device detects that the heart rate has fallen below a predetermined value, the pacer switches to a demand pacing mode and delivers pacing pulses to the heart.
A multiprogrammable, telemetric, implantable defibrillator is disclosed in the copending U.S. patent application Ser. No. 239,624 of Norma Louise Gilli et al., filed Sept. 1, 1988, entitled "Reconfirmation Prior To Shock In Implantable Defibrillator," which is assigned to the assignee of the present invention. This device contains a bradycardia support system as well as a high energy shock system to revert ventricular tachycardia to normal sinus rhythm. After reconfirmation of the presence of a tachycardia, high energy shock is delivered to the patient either at a predetermined time or when the desired energy level is reached.
Supraventricular tachycardias have been observed following termination of ventricular tachycardia by either cardioversion or antitachycardia pacing, as described in the article "Comparative Efficacy of Transvenous Cardioversion and Pacing in Patients With Sustained Ventricular Tachycardia: A Prospective, Randomized, Crossover Study" by Saksena et al. in Circulation, Vol. 72, No. 1, pp. 153-160 (1985). Termination with transvenous cardioversion was followed by occurrences of atrial fibrillation, atrial flutter, and sinus tachycardia.
Post cardioversion arrhythmias have also been observed by Saksena and Calvo, as referred to in the article "Transvenous Cardioversion and Defibrillation of Ventricular Tachyarrhythmias: Current Status and Future Directions" in PACE, Vol. 8, pp. 715-731 (1985). In this study, the incidence of supraventricular tachyarrhythmias after transvenous cardioversion was substantial.